Top burner thermostat



P 1959 L. B. WAGNER 2,903,890

- TOP BURNER THERMOSTAT Filed Dec. 14, 1956 INVENTOR.

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ATTORNEY LEL'AND a. WAGN R United States Patent O TOP BURNER THERMOSTAT Leland B. Wagner, Goshen, Ind., assignor to Penn Controls, Inc., Goslen, Ind., a Corporation of Indiana Application December 14, 1956, Serial No. 62%,282

1 Claim. (Cl. 73--368) This invention relates generally to temperature sensing elements and in particular to a temperature sensing or thermostat assembly adapted for mounting within the top burner of a domestic range.

Thermostats of the type mentioned above have in the past been characterized by a somewhat bulky and irregular configuration due to the placement of the resilient members or springs within the assembly to provide the required downwardly moveable mounting for the temperature sensing bulb which is necessary to assure proper heat exchange between the bulb and the bottom of a pan placed upon the burner.

In the present invention the assembly comprises a principal tube or sleeve the upper end of which is surrounded by a cylndrical shielding element of a diameter slightly larger than that of the tube.

The space thus provided between the shield and the sleeve is utilized to house a compression spring which retains the shield in proper position when there is no cooking utensil, or pan, in place on the burner. The space between the shield and the sleeve also provides an air passage which, along with openings in the lower closure member of the sleeve permit air to circulate by convection into these passages and then out of spaced, horizontally-elongated openings adjacent the upper margin of the shield. The openings in the shield are placed so that the convected air has the maximum cooling effect on the thermostat assembly.

These convection currents of air through the assembly appear to occur only under conditions of heavy load at relatively high temperatures, as for example with deep-fat frying. Under this condition the magnitude of the convected air is sufficient to provide a cooling efiect on the assembly 'which tends to compensate for the control error introduced by the accumulated heat in the assembly parts thus reducing the tendency of the sensing element to throttle the burner flame before the load has reached the desired temperature thereby desirably decreasing warm-up time. Under the opposite extreme Operating condition, i.e., light load at relatively low temperature as 'for example in simmering, the openings in the shield serve to admit radiated heat from the burner flame to the sensing element to cause a heat anticipating efiect, a throttlng of the burner at a lower load temperature than would be the case in the absence of heat radiated to the sensing element from the burner. Under this low temperature, light load condition the convection currents through the assembly are of small magnitude and insufiicient to detract to any effective degree from the effect of radiated heat on the sensing element. Under the heavy load, high temperature condition previously referred to the magnitude of the convected air appears to be suificiently large to overcome the efiect on the sensing element of radiated heat from the burner, this radiated heat, of course, being present under both previously mentioned extreme load conditions. The openings in the heat shield therefore appear to create Patented Sept. 15, 1959 both a desirable heat anticipating etlect under light load, low temperature conditions and to have a desirable cooling eiect on the sensing element under heavy load, high temperature conditions.

An object of the present invention is to provide a top burner thermostat assembly in which the Components are so placed as to provide an assembly of minimum size and maximum ruggedness.

A further object is to provide a top burner thermostat assembly having convection air passages which provide for both the maximum circulation of air over the assembly Components under heavy load conditions, and the admission of radiated heat under light load conditions.

These and other objects will become apparent as the description proceeds with relation to the accompanying drawings in which:

Figure 1 is a side sectional view of a top burner thermostat embodying the present invention mounted in' a closure member 12 which has air circulation openings 15 therethrough.

Member 12 may be mounted by means of bolts 13, or by any other suitable means, to a mounting flange 14 which may form a part of the stove top burner assembly (not shown). As shown mounted, the sleeve 10 extends concentrically through a conventional gas stove top burner 16, shown fragmentarily in Figure l, the disclosure including portions of the burner grate 25. The upper end of the sleeve 10 has formed thereon upwardly extending tabs 17, and a flanged margin 20. Surrounding the upper end of sleeve and of a slightly larger diameter is a cylindrical heat shielding element 18. The element 18 is held fioatingly mounted relative to the sleeve ll) by means of a compression spring 19 which extends between a spring receivng groove 21 in the element 18 and an annular Washer or spring retaining mernber 22 which, in turn, seats upon the flange 20. A snapring 23 which is urged against the underface of flange 18 by the force exerted by spring 19 limits the upward movement of the element 18 relative to the sleeve 10. Near its upper margin the element 18 has spaced, elongated openings 24, and its upper margin is formed to provide an inwardly turned circumferential flange 26.

A generally dsc-shaped temperature sensing bulb 27 has a marginal flange portion 28 adapted to cooperate With the flange 26. Extending from the under-face of the bulb 27 is a capillary tube 29 which is coiled within the sleeve and extends through the member 12 to a conventional power element or diaphragm which forms the controlling part of a thermostatic gas valve (not shown) which is located so as to control the gas owing to the burner '16. The capillary tube 29 is centered and held rigidly mounted within the closure member 12 by means of the conventional mounting assembly 31. The coiled portion of tube 29 which is housed within the sleeve lt) may be formed of a material having suitable resilience, such as stainless steel, and the coiled portion because of its shape provides an upward force on the bulb 27 serving to bias its flange 28 into engagement with the flange 26 on the element 18. From the foregoing, it will be apparent that with the bulb 27 and capillary tube 29 filled with a suitable temperature responsive fluid, any change intemperature at the bulb`--27; particularly at its upper face will-bereflected in a controlling movement of the valve, not shown, which Controls, the flow of gas to the burner 16.

When no pan or--other.;utensi1'is resting on the grate: members 25,` the thermostat assembly-will be inth'e posi- When pan^32-^-(Figure -3') is` placed on the burner, as will be evident fromFigure h the tion shown in Figure- 1.

bulb' '27 'will be lowered somewhat swith relation to the flange 26,' this movement being accommodated by: a

slight compression of the coiled portion of the tube-29',

further, the element 18 will be loweredto'thelevelbf the grate members 25; this movement-being-accommodated by compressionaof the spring l9 It will be apparent that this arrangement wherein thebulb-27 must be moved downwardly a slight amount relative to the element 18 whena pan- -s placed- 'upon v the- -burner assures that the upper face of the bulb 27 has good thermal contact with` the bottomof the pan;

Since accuracy of control of the temperature of 'the pan or utensl and its contents requires that the-bulb 27' rsponds only to the temperatureof 'the pan, it 'is important to minimize the temperature -build-up -ofthe partsof the assembly which are *adjacent tothe bulb 127,* under heavy load, high temperature conditions; T aidin minimizing the steady state temperature of these adjacent parts the openings 15 in the member-12 permit the entrance of convecton currents of` air' which travel up:

through the assembly and out of the-openings 24-`in the member 18. Since the element, 18 ismoved downwardly with reference to the sleeve when a pan or utensl isplaced upon the burner, the snap ring 23 will-be displaced downwardly somewhat from the-flange 20. The passage thereby created between the sleeve 10 and the element 18-- also serves to permit convecton currents of air to flow upwardly between element 18' and 'sleeve '10-` and to exit' through the openings 24..

The openings 24 similarly serve to admit heat radiated from the burner to the sensing element which 'is' effective,-

only under light load, low. temperature conditions, to

provide a heat anticipating efl`ect for the control'and to reduce control temperature over-run.

From the foregoing it` will be apparent that the pres cnt invention provides a top burner thermostat assembly having convecton air passages which provide for the maximum circulation of air over the assembly components, under heavy load, high temperature conditions, permits access of radiated heat to the sensing element under light load, low temperature conditions, and in-which the Components are so placed as to provide an assembly of minimum size.

than said sleeve surrounding the upperportion'- ofthe sleeve and extending beyond the---open end thereof; said shielding element having; an inwardly flanged upper margin; an abutment on said shielding element adjacent its lower margin, outwardly-extending flanges on said sleeve adapted to overlie said abutment; a compression spring housed within the space between said shielding element and said sleeve and extending between said shieldingelement and the outwardlyxextending-flangesonsaidsleeve,

said spring being thereby'adapted to retain contiguous theflanges on the-sleeve andthe--abutment-on the shielding element; a disc-shaped temperature sensingbulb adapted to. le within theupper end'of said fshielding-element and having aperipheral flange cooperating withthe margnal fiange on said shielding elementg resilient means extending between said closure member and "said bulb forurging saidlastmentioned-anges into `'contact with each other;- a source of radiantheat provided by the burner and' disposedannularlyaronnd said shielding-element, air circu--- lating means comprising a plurality ofhorizontally-elom gatedpassages in said shielding element adjacent its flanged uppermargin and complementaryair passages-insaid= :c1osure member whereby air, may` circulate by convecton into the passages in the closure member and into the space betweensaid sleeve and said;shielding element and then out of said passages in the shielding element, thedisposition of said `shielding element; passages being such as totprovide a linear .positional relationship between said' heat. source, saidpassages and' said sensing bulb whereby an unobstructed. pathfifonradiant heat exists from said source of radiant heat to` said 'sensing bulb.

References -Cited in thefile of' this patent UNITED STATES PATENTS( 947,914 Junkers Feb: 1, 1910 2,303,012 Weber- Nov. 24,'` 1942 Z,4 87,946 Senn Nov; 15, 1949' 2,534,097" Akeley Dec. 12, 1950' 2,699,487 Turner .Tani 11, 1955 2,786,930 Weber a Mar. 26; 1957 

